The goal of the proposed research is to obtain a better understanding of the organization and connections of the portion of the somatosensory system devoted to the teeth and oral cavity in primates. Preliminary microelectrode mapping studies in several species of monkeys have shown that lightly tapping the teeth activates two large, separate parts of the "primary somatosensory cortex" or "SI." In the present series of experiments we plan to (1) determine in detail how the teeth and oral cavity are represented in these two regions of cortex, (2) study responsiveness to both mechanical and electrical stimuli, and (3) use anatomical tracers to determine the cortical and thalamic connections of these two regions. The results of the anatomical experiments will be used to locate the regions of the thalamic relays and additional areas of cortex representing the oral cavity. The organizations of these regions will then be determined using a similar approach of mapping combined with injections of anatomical tracers into electrophysiological defined sites. Thus, the organization of the central representations of the teeth will be studied in a sequential manner beginning with the "primary" somatosensory cortex. Injections of anatomical tracers into regions of the thalamus representing the teeth will identify the sources for input from the trigeminal brainstem nuclear complex. These studies will provide a detailed understanding of the organization and connections of cortical and thalamic representations of the teeth in monkeys.